Improved High Power LED Bike Head Light With Integrated Heat Sink





Introduction: Improved High Power LED Bike Head Light With Integrated Heat Sink

After scouring the globe for the right parts, the following is an updated version of my copper fitting based LED bike head light. See the original high power LED bike head light with integrated heat sink instructable for the details on the earlier version. The latest incarnation uses a cheaper and more full featured driver circuit, an in-line waterproof switch, a waterproof connector, a more elegant mounting solution, a more robust and waterproof enclosure, and gets your whites their brightest.

Step 1: Materials

The bill of materials for this light is more extensive than previous incarnations, but the result is an improved piece of kit.

1x ~1.25" long section of 3/4" copper pipe
1x ~1" long section of 3/4" copper pipe coupling
2x 3/4" pipe cap
1x ~4" section of 12GA solid copper wire
Gear for silver soldering

1x Cable with Trail Tech connector
1x Waterproof cable gland
1x 3-mode boost constant current driver
1x 2 Ohm resistor in 1206 or 805 surface mount size
1x LiFePo 6.4V battery pack
Misc wire for connecting driver to LED
Gear for electronic soldering

Light engine:
1x Rebel Endor star 3-up or 1x Cree XPG Indus star 3-up
1x Lens for Endor 3-up
Thermal epoxy

1x 5/8" x 6" Velcro face strap

Step 2: Housing

Building the housing well is the key to a watertight and pleasantly distressed final product.  Don't be afraid to drip solder, leave file marks, and otherwise individualize your light.  Remember, bones heal, chicks dig scars, and the US of A has the highest doctor to daredevil ratio in the world.  I don't know what that has to do with anything, but go nuts.

Similar to the last light project, you will need to trim down a pipe cap and drill holes in it to mount and wire the LED star. Leave a light shoulder on the pip cap protruding beyond the lens to protect it from damage, 2mm is fine.

The lengths of the 3/4" pipe and coupler section aren't critical. You'll need to have the smaller 3/4" pipe section stick out of the coupler enough to epoxy on the rear cap, about 1/4" is fine.

Take a section of bare 12GA solid copper wire and bend it up as shown in the photos using your hands, feet, and teeth or a handy pair of jewelers pliers.  This wire will serve as the mount.  Size it according to the handlebars on your application.

Test fit everything before soldering.  Then deburr, sand, clean, and flux the LED pipe cap, the coupler section, the inner 3/4" pipe section, and the wire cleat.  Use a clamp to hold the pipe cap and other tubes in place while you heat and solder.  Balance the cleat on the top and solder it while the rest is still hot.

The back cap has to be the last to go on and can't be soldered since there are sensitive electronics on board at that point.  You will want to drill a hole in the back pipe cap to hold the waterproof cable gland and trim the length of the pipe cap to match the amount of reveal you left on the 3/4" section of pipe.  Depending on the size of the cable gland nut you might need to trim the nut or leave more pipe cap to get it to fit.

Step 3: Modify the Driver Circuit

The driver circuit I used for this light is much cheaper than the BuckPucks and has more features. The downside is that it is poorly made in China. Also, Chinese manufacturers have taken to sanding the identifying marks off of the IC's in their circuit boards from DX (I do not take your name in vain oh holy and almighty DX). I am not sure why they go to the trouble. I guess they figure that if they can whip up a knock off of the IC manufacturer's application example circuit from the datasheet then so can anyone else if they could just read the IC markings. But wait! They have cleverly sanded the markings off so you have to page through a few dozen datasheets to identify their circuit. They have obviously been to B-school and have heard the term "barrier to entry".

Ok, that is a long way of saying that I figured this out so you primitive screwheads don't have to. I mean, things with molecular structures and everything. The driver is based on the FP5138 ( boost driver.

The three modes on the driver are specified as 800mA on high, 200mA on low, and 400mA strobe. Since the "specs" on such products from DX are not very tight and seem to be in direct contradiction to the helpful formulas provided by the IC manufacturers, I went ahead and measured the currents myself. The measured currents are 1200mA on high, 250mA on low, and strobe just duty cycles high. Your mileage and circuit revision may vary. The currents are set via resistors which are difficult to reach and thus our task is to cut the two circular PCBs apart and swap the resistors and then solder the two boards back together. The smaller top PCB is the driver board, and the larger bottom one is the microcontroller that sets which resistor is being used via some transistors.

The resistor we are looking for was a stack of two in my boards, an 0.820 Ohm and a 4.7Ohm which gives 0.7 Ohms. This is the high resistor. The low resistor is a 2 ohm. I chose high to be 500mA and Low 250mA. This is to increase battery pack life and to cut down on thermal stress on the assy. To accomplish this, remove the 0.820 Ohm and 4.7 Ohm resistor stack and replace with a 2 Ohm resistor. See the picture. Solder the two boards back together and you are done.

Step 4: Put It All Together

Take the wires for the LED and solder them to the LED pads, thread them through the holes in the LED pipe cap and solder them to the driver circuit.  You'll want to use a fairly thin wire so you can wind up the excess and insert it into the cavity.  With the LED soldered up, use some jumpers to connect a battery to your driver circuit and briefly test to ensure that the LED lights as desired.  To switch modes on the driver, you need to cycle the power.  Make sure everything works before buttoning it all up.

With everything working, use the thermal epoxy to glue the LED to the bottom of the pipe cap.  Be sure not to get the epoxy up onto the top pads since it is also electrically conductive.  When that is cured, epoxy the lens in place on top of the LED star.  Don't use the conductive epoxy in case it gets somewhere you don't want it.  I use JB Weld in these cases.  When the lens is cured in place, take some silicone sealant and seal the lip of the lens against the pipe cap to keep water from getting at the LED.  Try not to get anything on the face of the lens, and if you do, wipe it up before it cures.

Mount the waterproof cable gland in the rear pipe cap, and thread the cable through the gland and tighten everything.  The gland should come with an O-ring that seals against the housing, but if you lose this, use some silicone in there to seal it during assembly.  Take the loose ends of the wires and solder them to the appropriate pads on the back of the driver circuit.

Next, take the driver circuit, wrap it in electrical tape and goop it up with silicone sealant and cram it into the housing.  Let the silicone cure before gluing on the rear pipe cap.  Now would be a good time for another system test prior to sealing.  With everything functional, mix up some thermal epoxy and glue on the rear pipe cap, sealing your light forever.

To attach the velcro, measure your velcro strapping and cut to desired length.  The idea is that one end of the velcro will be permanently attached to the light at the wire cleat and the other will wrap around the handlebars to the other section of wire cleat and loop back on itself to latch.   Get everything ready and use some hot glue to fuse the end of the velcro around one end of the wire cleat. See pictures.

With your battery of choice (I chose a LiFePo battery as linked in the BOM) you are good to go.

Step 5: Final Thoughts

I hope the preceding has been helpful for those of you looking to build better lights than are commonly available on the market today.  I'm in the process of adapting this design to the latest in high efficiency LEDs, which promise another 20% or so in performance.  Good times.  Feel free to contact me with questions or post to the discussion below.

I've also been approached by some folks who don't want to go to the trouble of building this light and wish they could buy one complete or failing that, a kit.  Depending on the person and my bandwidth at the moment I have alternately obliged them or castigated them while buffeting them about the head.  For those of you with similar ideas, feel free to contact me, although my prices are exorbitant.



    • Oil Contest

      Oil Contest
    • Make it Move Contest

      Make it Move Contest
    • Woodworking Contest

      Woodworking Contest

    We have a be nice policy.
    Please be positive and constructive.




    I have this Battery that was hoping to use to drive my DIY lights. wondering if plans listed above would work ? if not possible suggestions

    5 v with 2.5 amp output with total of 10400 mAh


    I'm a bit daft with these things, so if anyone is willing to build me one of these bike lights I am happy to pay them.



    Nice work, just want to get an update, are you using the same bulb or have you upgraded?
    would bulb like these work with your driver?

    4 replies

    I've used the XML's (on this motorcycle e.g.) but not the XTE's.  XML's are the best available and due to their large die size have much better thermal performance. No multi-LED stars though so you need to run a single XML at high current which is a bit of a challenge since the cheapo drivers are not usually up for running 3000mA.

    We'll see if I can find the time to document some XML bike lights in the future. Basically it is the same as above except you use a single lens and difference driver.


    Thanks for the reply, I am using this driver to run 2 xml's in series.
    I am going to us part of your design and a few others, am working on brazing fins to the copper tube as well as a few other idea's.
    Thanks for all the work you have done and posted

    different driver

    Or this one?

    I really love the design of this. Very helpful instructable. I would be really interested in running this light off of a 6volt 3 watt hub generator, and possibly adding a capacitor for a stand light. Any tips.

    1 reply

    You'll need a different driver, a boost mode (like the one pictured in step 3) rather than buck mode ( like the one pictured here: ) driver since the Vf of the 3 LEDs in series is greater than 6V. Most of the boost drivers available cheaply on DX are multi-mode, meaning the have hi, lo, strobe, etc modes that are cycled through by turning on and off rapidly. The problem with this on a generator driven setup is that when your capacitor stand light accumulator drops too low, the light will cycle the mode, so that when you start again the mode might be strobe, or even off. Kind of a pain.

    Also, for a generator light, you'll probably need to set the current even lower unless you typically ride fast (>15mph). I lowered the drive current to 500mA on high for about 5W. You'll want to get down to around 3W, or 350mA. The good news is that you should still be able to get 350 lumens or so at 3W, and it will run cooler.

    I am having a bit of trouble getting the stuff from batteryspace as the postal charge is nearly $80! This kind of makes the whole thing pointless for me as I am sure I can find a bike light as bright for less than the total cost. Unless I can get these parts here in the UK. So, I have 2 questions:
    1. I don't really know what i'm doing so may need help on a battery pack and what to do to the driver as a result. 3x good UK sites are:, and
    2. What do I use to charge this? I do have a multi power adaptor unit which has a volt selector for 1.5,3,4.5,6,7.5,9,12 volts.

    10 replies

    The battery pack you'll need depends on the driver as well as the LED and planned usage. I'll assume you are using the XPG 3-up star with a Vf of around 10V and max current to the LEDs of 700mA. If you are going with the multi-mode driver I specified, you will need a battery pack with less than 8VDC and 7Wh capacity for each hour of max current runtime. Watt-hours (Wh) can be calcuated by multiplying the nominal battery voltage by the amp-hour rating (Ah or mAh). In the case of the specified 6.4V 2400mAh battery pack, the Wh rating is 15.36Wh.

    If you use a buck type driver (like the 13557 driver from DealExtreme) you will need a battery pack with more than 12VDC with the same Wh rating.

    The charger will depend on the chemistry. Your multi-power adapter unit doesn't sound like a charger so I wouldn't use it for any battery. Lithium battery packs will require a lithium charger for safety and longevity. NiMH and NiCd will work with the same charger in most cases.

    Use any source you feel comfortable ordering from to pick a battery pack and charger and I can take a look at it before you buy. I don't have the time to do your shopping for you unfortunately. I'd suggest a radio control hobby store as a good place to look. Or you can bundle a bunch of regular AA type cells together.

    Thanks for the explanation. I am a little unclear. You say if I use your driver (your link provided in the shopping list) I would need less than 8VDC and 7Wh capacity for each hour of max current runtime. But the battery you are using is 6.4V 15.36Wh which has a higher Wh rating.

    I did find this:

    Will this work?

    My aim is to get maximum brightness for minimum 2-3 hours.

    Yes, the battery pack I listed has 15Wh of energy. Supplying 7W of power to the LEDs this will last a little over 2 hours. Since the power of the LEDs at the "high" setting is about 7W, you will need at least 7Wh of energy in your battery pack for each hour of runtime. If you want max brightness for 3 hours, you will want to find a battery pack with more than 3h x 7W = 21Wh.

    The pack you linked is 6V x 1.6Ah = 9.6Wh which will only run on high for 1.3 hours or so.

    The thing I am still a little unsure about is where you remove and add in a resistor to the driver. If I use a 7.2V 4200mAh battery then that's a very similar Wh to your battery but with a higher voltage. Will this be ok? Do I still need to mod the driver?

    I found more batteries:


    or will it be brighter with a 7.2V? I have a battery and charger like this one already:

    Not sure what to calculate. Thanks.

    As I said, the Wh can be calculated by multiplying pack V and Ah.

    For the first link, this would be 6V x 2Ah = 12Wh. Divide by the load wattage (7W) to get about 1.7 hours of runtime. I'd also mention that used battery packs are a bad idea as you have no way to know the pack condition and lifetime.

    The second pack is 6V x 3.3Ah = 19.8Wh and thus 2.8 hours of runtime.

    Both of these packs are suitable for a boost type driver for the star board with 3 LEDs in series (Vf = 10V)

    EDIT: Seriously? You have been pestering me with all this and you already have a battery pack and charger? I suggest you use it. Over and out.

    I did speak to them about the lens and they advised the Elliptical to get a good mix of spot and wider light spread. What do you think? Also, can I use XPG stars in this spec above? Which on and where do I buy it?

    The focus on the 3-up lenses LEDSupply carries when used on the XPG is pretty wide to begin with. The elliptical is ~44x23 for the XPG and the narrow is 24 FWHM. When using the elliptical lens you will have to plan the orientation of your LED star as well as the lens in advance and then solder the housing correctly to allow the long axis of the elliptical pattern to align with the ground. Not impossible but in my opinion is unnecessary. This is due to the fact that with 44 degrees of half magnitude spread, the light will have very little throw and the effective candelas at a given point will be low and thus your visibility poor. Even the "narrow" conical lens at 24 FWHM is really a bit too wide for an all-around trail bike light and would be best supplemented with a head mounted light with a tighter beam and more throw to give better long distance visibility. For street riding, the narrow is good, but when doing a mountain bike trail at night you'll want some more throw when descending at speed. For that, I use a single XML with the tight 7 degree FWHM lens.

    Thanks for all that I have gone with your recommendation. Just one thing. The link to the battery pack seems to be out of stock. What batteries are these? Is there an alternative?

    The listed 6.4V pack with connectors is really the best match and since it includes the connectors is really the best deal pricewise. If you can't wait for it to be in stock then the next closest match is a slightly bigger 6.4V LiFePo pack without the connectors. You'll have to buy the connectors separately and solder them on yourself.  A good coating of "tool dip" once complete is a good idea as well.

    Good luck